A variety of print inspection devices and methods have been proposed. In one such method, tone marks or color patches printed in the marginal portion of prints have been inspected to determine the acceptability of the prints. Devices and methods have been proposed in which data has been obtained from a printed pattern by utilizing a single sensor to input the data of the entire area of the printed material. Other devices utilize various scanning methods; however, these methods do not monitor large area print with high accuracy. Additionally, such methods require a large amount of data to be processed and are not sufficient for large area print inspection at high data rates.
Other methods for print inspection involve a comparison system in which reference data is compared with scanned surface data to determine the print acceptability. A comparison system in which reference data is compared with the previous inspection data again requires a large amount of processing time which is not compatible with present day high speed rotary printing presses.
A need has thus arisen for a print inspection method for monitoring the ink density levels of newsprint areas and detecting defects within those areas which can be accomplished at high printing press speeds and which compare actual measured values against a set of internal or user criteria.